15/01/2008
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The individual hallmark of the car.
In the field of rim production Austria Alu-Guss relies on OvalFlex from CERATIZIT. Including interview with customer!
Its design is the eye-catching feature of a car, providing it with a personal touch: the aluminium rim. It is en vogue as never before, and almost every automobile today has aluminium rims as a standard feature. The variety of types and design is continuously increasing. OvalFlex, a modular turning tool developed by CERATIZIT, fulfils the demands of the manufacturers regarding flexibility, productivity and process security. The CERATIZIT customer Austria Alu-Guss, who is one of the big players in the sector (production volume of three million aluminium wheels per year) has successfully applied OvalFlex since the beginning of 2007.
The tendency: exclusive styling
Light metal wheels are applied in formula 1 cars, trucks for heavy load transports and also in the aerospace industry. The major share however are aluminium wheels for automobiles where basically two types may be distinguished: one-piece rims in one casting and multi-piece rims which are connected by screws and consist of a rim bed, a rim crown and a centre hub.
Austria Alu-Guss is based in the Austrian Ranshofen, has been a member of the Borbet group since 1996 and develops and produces aluminium rims for Audi, BMW, Mercedes, Opel, GM, Porsche, VW, Seat etc. The company has 730 employees and offers wheel types with annual quantities over 100,000 pieces as well as small batches of less than 1,000 pieces. The trend is towards smaller batch sizes whereas the styling is becoming increasingly varied. “The most important task is to technically implement the customer’s wishes regarding the design,” says Alois Grömer from the mechanical machining department at Austria Alu-Guss. “A light metal wheel almost always represents a compromise.”
Stability and high performance: OvalFlex
On a conveyor belt the blank aluminium rim is transported to the CNC machine, where it is turned at around 2000 rev/min applying OvalFlex.
OvalFlex has exclusively been developed for machining light metal wheels. The oval shape differs from the conventional round shape of copy turning tools. In this way the tool does not need so much space and can go deeper into the rim. The height however has remained the same and guarantees stability which increases profitability, as high stability makes larger depths of cut possible.
The main attraction: the new oval interface connects the tool shank with the tool head. Four tapered surfaces around the interface provide accurate connection with the location face in both radial and axial direction. Thanks to this highly precise connection it is almost unnecessary to make corrections.
High flexibility, reduced logistics
Another advantage of OvalFlex is its modularity. Different styles of tool heads can be mounted on the adapters. In addition, different angles can be set on the tools. A system which ensures that aluminium wheel manufacturers benefit commercially and logistically, as thanks to modularity they need fewer special tools and the necessity for stock keeping is decreased.
Exact positioning of the inserts
For Ovalflex CERATIZIT has developed new inserts. The X32 insert is larger than the common inserts and extremely stable. Thanks to its top faces it may be positioned precisely, assuring that the insert also absorbs the cutting forces better. The X32 insert is even protected against drawing cuts in the best possible way through the shape of the top surfaces.
The steps in the manufacturing process of light metal wheels:1. High-quality metal is melted and the respective alloy formed so that the wheels can be cast in low-pressure machines.
2. An x-ray facility checks every wheel for faults in the casting.
3. A heat treatment taking several hours increases the strengths of the wheels.
4. The wheel profile is turned on CNC machines, subsequently the valve hole and the holes for the bolts are drilled. Everything is done with tools from CERATIZIT.
5. All wheels are checked for unbalance, cleaned and then finished with lacquer. A 3-layer structure of the lacquer protects the wheels while being used.
6. Finally a fully automatic helium pressure test facility verifies if the wheels are leak-proof.
Interview with Alois Grömer from the mechanical machining department at Austria Alu-Guss:
Which step is the most tricky when manufacturing aluminium rims?
Grömer: “This depends on the design. In general you could say that a combination of all processes leads to a good product. When producing a wheel made of easy-to-machine material there may be problems during casting. But then, with a wheel that can easily be cast, there may be problems during machining. Various special lacquers may also cause problems during production.”
What is important with regard to the hard metal?
Grömer: “We have to find the ideal composition of the carbides. The higher the silicon content in the aluminium alloy, the faster wear occurs.”
What was the most complex rim you have ever produced?
Grömer: “It was a Rolls Royce rim, a so called ‘Nature Wheel’ which was very difficult to machine because of its thin walls.”
What is the tendency in the aluminium wheel sector?
Grömer: “The tendency is towards individuality and light construction. The unsprung masses have to be reduced, this means a consistently light construction of the wheels."
How long does a cutting insert last on average?
Grömer: “It is very difficult to make a precise statement as the service life of an insert depends on numerous factors. By rule of thumb however you can say that a cutting edge can work up to 400 rims (standard rim 17 inches).”
What is CERATIZIT's strength?
Grömer: “CERATIZIT has always been one of the leading companies in the field of aluminium machining. With the recently developed modular OvalFlex tooling system CERATIZIT has succeeded in offering a completely new and stable system which shows great performance capacity and flexibility. This is where I can see an essential advantage compared to competitors.”
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